Flatness deviations in the photoresist substrate and the photomask and other gapping or focusing parameters are a significant factor in non-contact photolithographic methods. The deviations in the gapping or focusing of the photoresist substrate contribute to poor photoresist images, linewidth non-uniformities and erratic step coverage by the photoresist material. Heretofore, techniques for determining gapping deviations between the photoresist substrate and photomask in the proximity printing art or focus deviations in the projection printing art have been detected by errors in the end product after much time and effort has been put into its development. Optical microscopic techniques and scanning electron microscope techniques are used to identify to some extent the deviations causing these problems.
There is a need in the art for a method of quantitatively determining deviations in the photosubstrate or photomask affecting the developed resist image from a photomask.